Among switching devices such as circuit breakers, there exists a switching device in which, upon closing, restoration force exerted by a spring is utilized in order to rapidly and steeply perform the closing operation, or more specifically, the approaching operation of a movable contact to a fixed contact; the movable contact and the fixed contact configure a contact point (main contact point) In a switching device of this type, prior to the closing operation, the closing spring is energized by contraction or tension and the closing spring is restrained in this state; upon the closing, a contact closing lever, connected with the contact, is operated through restoration force exerted by the closing spring that is released due to cancellation of the restraint so that the movable contact is moved at high speed.
Various kinds of configurations of an energy storage mechanism for storing energy in the closing spring have been proposed along with various kinds of configurations of a stored-energy release mechanism. FIG. 7 is a side cross-sectional view illustrating the principal parts of an energy storage mechanism disclosed in Patent Document 1.
The energy storage mechanism is provided with a main shaft 1, an energy storage shaft 2, and an energy storage motor 3 that are commonly supported by a supporting frame 4 in such a way as to be approximately parallel to one another. The main shaft 1 holds in a fitting manner a large gear 5 at the protrusion end thereof protruding from one side of the supporting frame 4 and a closing cam 6 at the middle portion thereof; the large gear 5 and the closing cam 6 rotate on the main shaft 1 as the main shaft 1 rotates.
On the outer side of the large gear 5, a crank pin 7 is provided in a protruding manner at a position that is eccentric by an appropriate distance from the center axis of the main shaft 1. One end of a press rod 8 is coupled with the crank pin 7; the other end of the press rod 8 is supported in an insertion manner by a spring plate 9. The spring plate 9 is a fixed plate that is integrally provided in a protruding manner, for example, at the outside of the supporting frame 4; a closing spring 22 is inserted between the spring plate 9 and a press plate 10 that is fixed to the middle portion of the press rod 8.
As illustrated in FIG. 7, when, due to the rotation of the large gear 5, the protrusion portion of the crank pin 7 becomes close to the spring plate 9, the closing spring 22, inserted between the spring plate 9 and the press plate 10, is contracted, thereby storing energy. The foregoing energy storage state is maintained by restraining the rotation position of the large gear 5 by unillustrated restraining means; when the restraint is released, the spring force by the closing spring 22 is exerted on the large gear 5 via the press plate 10, the press rod 8, and the crank pin 7, so that the main shaft 1 rotates at high speed, along with the large gear 5.
Inside the supporting frame 4, a contact closing lever 11 is pivotably supported through the intermediary of a supporting axle 12 that is provided in a protruding manner at one side thereof. On the other side of the contact closing lever 11, there is supported a roller 13 that makes contact in a rolling manner with the cam surface, i.e., the circumference of the closing cam 6; through the operation of the roller 13 that follows the cam surface, the contact closing lever 11 pivots on the supporting axle 12 in accordance with the rotation of the closing cam 6; the contact closing lever is connected with an unillustrated contact in such a way as to perform closing operation through the pivoting.
The energy storage shaft 2 is provided with a transmission gear 14 that is integrally fixed to the protrusion end thereof protruding from one side of the supporting frame 4 and a driving gear 15 that is loosely inserted between the transmission gear 14 and the outer surface of the supporting frame 4. The transmission gear 14 is engaged with a large gear 5 fixed to the end portion of the main shaft 1; the driving gear 15 is engaged with an output gear 16 into which the output end of the energy storage motor 3 is inserted.
The energy storage motor 3 is a geared motor in which the rotation of a motor main body 3a is outputted after being decelerated by a speed reducer 3b consecutively arranged at the output side of the motor main body 3. An output shaft 17 of the speed reducer 3b is inserter into the output gear 16; a one-way clutch 18a that allows rotation only in a single direction is inserted between the output shaft 17 and the housing of the speed reducer 3b. 
Via a nail clutch 19 and the one-way clutch 18b inserted into a hole that penetrates the center axis portion of the driving gear and holds the one-way clutch 18b, the driving gear 15 engaged with the output gear 16 fits around the energy storage shaft 2, in such a way as to be relatively rotatable and slidable in the axis direction of the energy storage shaft 2; the driving gear 15 is biased toward the transmission gear 14 by a press spring 20 inserted between the outer surface of the supporting frame 4 and the driving gear 15. The one-way clutch 18b provided in the driving gear 15 allows rotation in the same direction as the one-way clutch 18a provided in the speed reducer 3b allows, and conveys the rotation, of the driving gear 15, transmitted from the output gear 16 to the nail clutch 19 inside thereof. On the other hand, in the case of the reverse rotation transmitted from the nail clutch 19, a slide is caused.
In normal time, the driving gear 15 is pressed against the transmission gear 14 through spring force exerted by the press spring 20 that elastically makes contact with the outer surface of the supporting frame 4 and rotates along with the transmission gear 14 through the engagement operation of the nail clutch 19. The foregoing engagement state is released in such a way that, when the main shaft 1 and the large gear 5 are situated in the respective rotation positions illustrated in FIG. 7 and energy is being stored in the closing spring 22, the driving gear 15 is pressed by a press protrusion 21 provided in a protruding manner at a position, on the other side of the large gear 5, that is approximately and radially symmetric with the crank pin 7, whereby the driving gear 15 resists against the spring force exerted by the press spring 20 and departs from the transmission gear 14.
In the conventional energy storage mechanism configured as described above, when, in the state illustrated in FIG. 7, the restraint of the large gear 5 is released, the large gear 5 rotates at high speed in a predetermined direction (the same as the direction in which the closing spring 22 is energized), due to the release of the restoration force exerted by the closing spring 22; this rotation is conveyed to the contact closing lever 11 via the closing cam 6, whereby the contact closing lever 11 pivots at high speed, so that the unillustrated contact is closed.
During the foregoing closing operation, the rotation of the large gear 5 is conveyed to the transmission gear 14 that is engaged with the large gear, so that the energy storage shaft 2 rotates; however, because this rotation direction causes a slide of the one-way clutch 18b incorporated in the driving gear 15, the driving gear 15 does not rotate, whereby the rotation force is not conveyed to the output shaft 17 of the energy storage motor 3.
While, due to the inertia of the large gear 5, the rotation, of the large gear 5, caused by restoration of the closing spring 22 continues in such a way as to exceed a predetermined rotation position (top dead center), the closing spring 22 is energized; thus, the large gear 5 and the main shaft 1 try to reverse the rotation after the top dead center has been reached. However, this reverse-rotation force is conveyed to the one-way clutch 18b incorporated in the driving gear 15 via the transmission gear 14; due to the engagement of the one-way clutch 18b, the reverse-rotation force is conveyed to the driving gear 15; and the reverse-rotation force is further conveyed to the output shaft 17 of the energy storage motor 3 via the output gear 16, and the one-way clutch 18a that is mounted around the output shaft 17 is engaged with the output shaft 17. As a result, the reverse rotation is hindered, and the large gear 5 is restrained at the rotation position where the large gear 5 has reached the top dead center.
When, after the foregoing closing state is obtained, the energy storage motor 3 is driven to rotate, this rotation is conveyed to the driving gear 15 via the output gear 16 fit around the output shaft 17; the rotation is further conveyed to the transmission gear 14 via the nail clutch 19; and the large gear 5 engaged with the transmission gear 14 rotates. Due to the rotation of the large gear 5, the press rod 8 coupled with the crank pin 7 is depressed; the closing spring 22 between the press plate 10 and the spring plate 9 is contracted, and the illustrated energy storage state is obtained; as a result, there is prepared a state in which the next closing operation is allowed. At a predetermined rotation position of the large gear 5, the press protrusion 21 presses the driving gear 15, thereby releasing the engagement of the nail clutch 19, so that the rotation, of the large gear 5, caused by the rotation of the energy storage motor 3 is interrupted; the predetermined rotation position is maintained through the restraint of the large gear 5 by the restraining means.
(Patent Document 1) Japanese Patent Application Laid-Open No. H11-40010